The invention resides in a laser machining apparatus and a method for forming a surface on an unfinished product. In particular, one or several cutting edges, chip surface areas and free surface areas are to be formed on the unfinished product. The surface area to be formed may be for example a chip or open surface. With this manufacture of the surface at the same time the edge, in particular the cutting edge can be formed. In this way from the unfinished product a cutting tool can be made. The unfinished product may also comprise several material layers or several elements attached to one another.
For machining once unfinished products, several ablation methods are known, for example, grinding. The grinding of very hard material, for example, polycrystalline diamond (PKD) or CVD diamond (chemical vapor deposition) has technical as well as economical limits. The laser ablation with the aid of shortly pulsed lasers offers more possibilities to economically machine these materials in order to manufacture for example tools.
The manufacture of high-quality cutting edges however is problematic. In the state of the art, laser systems are known which move along the contour of the unfinished object with the aid of a laser scanner, while the object is arranged stationary with regard to the scanner. Although this permits the laser scanner to operate at high speeds at which the individual laser beam pulses can be moved along the unfinished object, the accuracy achieved in the process does not comply with today's requirements. In addition, the surface areas and edges manufactured in this way deviate from straight lines and rather provide for an uneven, jagged shape.
Furthermore laser machining apparatus are known, wherein the laser is moved relative to the unfinished object via apparatus axes. In this way the accuracy and the quality of the surface areas and of the edges obtained on the unfinished object can be improved, but the ablation rates that can be achieved are small. The reason herefor is that the dynamics and the speed of the machine axes are limited. An increase of the dynamics of the machine axes requires large efforts and expenses which makes the laser machining fixture very expensive.
A method and an arrangement for the laser-machining of an unfinished product are known, for example, from DE 299 08 585 U1. The arrangement includes a laser for generating laser beam impulses via a drive unit, the laser and/or the object support structure are moved in a direction transverse to the optical axis of the laser. The laser beam is moved in the process in several adjacent or overlapping lines over the whole width over the area to be ablated for ablating individual material layers. The material is ablated dot-like at the contract points of the laser beam impulses. In order to achieve a continuous material ablation the contact dots overlap by 5 to 25%. In connection with pulsed lasers having a very high frequency correspondingly large advancing speeds are therefore necessary. As already pointed out the ablation rate is small in this procedure and the working times are correspondingly long.
WO 2006/038017 A2 discloses two different embodiments of a laser machining arrangement. In the first embodiment, using a laser scanner, an impulse area is formed from several adjacent impact points of the laser beam impulse. The material ablation occurs at the impact locations of the laser beam impulses of the impulse area. In a second embodiment no real ablation is provided but the unfinished product is cut apart. First the unfinished product is pierced. After the piercing, an advancement movement is initiated for cutting the unfinished product without interruption. This corresponds to the earlier described variants of the laser machining.
DE 10 2007 012 815 A1 discloses a method wherein the impact locations of the laser beam impulses are selected along a pattern by means of a scanner. Additionally, a one or two dimensional relative movement between the pattern of the impact points and the unfinished product may be executed. This superimposed relative movement is to be faster then the path movement of the laser impulses along the scanner path. How such a fast superimposed movement can be generated is not disclosed. The machine axes known in the art are not capable of accomplishing this.
It is the object of the present invention to provide a method and a laser machining apparatus by which the formation of accurate surface area and edge pattern can be established in an economical manner.